hi im having the same problem ive gone through 2 sets of plugs already at $15 a plug its very expensive if im standing behind the bike my left exhaust is missing and skipping, this is the top cylinder right? when i replaced the plugs it went sweet for about a month then i pulled em out and sam as you ther fouled, black adn full of fuel, i also run it dry off the fuel and never use the choke as fear of fouling plugs? any solution to the problem would be great.. i think there must be some sort of fuel leakage or running to rich on one cylinder ,.. any ideas how to adjust this .. these plugs are costing me more than petrol!!